1. Field of the Invention
The present invention is directed to conveyor systems, and more particularly to systems for facilitating loading of conveyors.
2. Description of Related Art
Conveyors are used to transport goods and packages in all types of environments and experience especially heavy use in manufacturing and shipping industries. In addition, characteristics of the flow of goods and packages along such conveyor systems, such as timing and positioning of the goods and packages, must often be tailored to the needs of the manufacturer or shipper. Accumulator conveyor systems are divided into zones in which a driving force may be selectively applied to a conveying surface which provides each package with a stopping position. As a result, packages or goods may be accumulated in successive zones for eventual discharge from the conveyor.
As an example, U.S. Pat. No. 5,862,907 to Taylor (“Taylor”) discloses an accumulation conveyor 10 that is divided into a plurality of accumulating zones A, B, C, D and E, as shown in FIG. 1 of Taylor. The conveyor 10 includes a conveying surface, in this case a plurality of rollers 14, that are selectively driven under the control of a plurality of accumulation modules 20A-E that correspond to the accumulating zones. Each module 20 is capable of communication with its neighboring or adjacent module in the upstream and downstream directions through communications cables 42A-E. Photoelectric or ultrasonic sensors 28 are used to determine the presence or absence of an item or package within each of the accumulating zones. Thus, when a sensor fails to detect a package in a downstream zone, its module communicates with the upstream zone to activate its conveying surface and convey an object held therein to the downstream zone.
Despite improvements in the control systems of conveyors, conventional conveyors have other areas in which improvements are needed. For instance, when a driver places a package or load with a forklift on an infeed conveyor zone, a sensor at the downstream end of the zone detects the placement and wakes up the zone. The rollers of the zone then begin to turn as the load is lowered onto the conveying surface. This has the drawback of putting pressure on the sides of the forks of the forklift, making it difficult for the forklift to disengage from the load. In another scenario, the forklift is placing the load into an intermediate zone which adds the complication of possibly having an upstream load move into the intermediate zone.
One conventional way to avoid these problems is to apply a zone stop signal to the module that controls the loading zone and the upstream zone, if one is present. This requires the zone stop signal to be activated in some manner, such as through a photoelectric eye aimed horizontally across an approach path of the forklift. The zone stop 1) stops the rollers in the loading zone and 2) stops the upstream zone (if present) from conveying the load into the loading zone. Backing the forklift away from the conveyor unblocks the photoelectric sensor allows the conveyor to commence normal operation.
However, the photoelectrical eye must often be installed in several zones as an aftermarket assembly with external controls and wiring. This can be a complex and expensive undertaking.
Therefore, it would be advantageous to have a conveyor and loading zone system that provides for loading at multiple zones of the conveyor without extensive external controls and wiring. It would be further advantageous if the loading zone system were operable with a zero-pressure accumulation conveyor system.